Lessons learned from Webber's DNF at last round's US Grand Prix due to yet another alternator failure for the team have spurred Red Bull's garage into action as Vettel looks to stave off Ferrari's Fernando Alonso and claim a hat-trick of titles at Interlagos.

Vettel holds a 13-point lead over Alonso ahead of the season finale and will be champion if he finishes in the top four, even if Ferrari's ace wins at Sao Paulo on Monday, Australian time.

But Webber admitted the team's consistent mechanical problems had ensured the championship was far from decided ahead of this weekend.

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His retirement at the US Grand Prix was the team's third this season due to alternator dramas - the previous two striking Vettel.

"It would be good to have a smooth weekend with no issues," said fifth-placed Webber who won last year's season finale in Brazil.

"A clean start and the car running smoothly for the whole weekend - then I'm sure we can finish the season very strongly."

Webber's retirement could not stop Red Bull sealing their third straight constructors' crown with one race left.

And a new alternator from engine supplier Renault should ease worries this weekend.

Ironically, other Renault-powered teams used the newer item without fuss in Texas while Red Bull felt safer using the older specification.

Asked why that decision had been made if the newer units had passed all reliability tests, Renault spokesman Remi Taffin said: "Because they are human beings and at some point as humans they have some feelings.

"Sometimes you go into a shop and there are two different things and your head says you should buy this one but your heart says you should buy the other one."

Red Bull chief Christian Horner said he hoped fortunes would change.

"We just have to approach the race as we have the previous 19," he said.

"We have to go there, attack the weekend and get the best out of ourselves, the car, the strategy, the drivers and reliability.

"Anything can happen, as we have seen this season. But it is good to be going there with a lead, and we go there determined to close the job off."

Two-time ex-champion Alonso has oozed cool leading up to the finale, hinting that the championship is Vettel's to lose.

"In Formula One there's always pressure but definitely we have less than if we were leading the championship," he said after finishing third in Texas.